Retinoids (vitamin A), besides playing pivotal roles in the visual process as well as in the function of the purple membrane (the proton pump of Halobacterium halobium), have recently been shown to be potentially useful as chemotherapeutic agents in cancer and in skin disorders such as acne. The heart of the proposal concerns the synthesis of structurally and geometrically isomeric allenic retinoids and their rearrangement to various sterically hindered natural and unnatural retinoids: 7-cis, 7,9-dicis, 7,11-dicis, 7,9,11-tricis, 9,11-dicis and 11-cis-retinals; their corresponding alcohol and carboxylic acid derivatives; deuterated derivatives of 11-cis-retinal; novel hydrogen shifted isomers; and various other analogs. Rearrangement reactions which will be examined include stereoselective and/or specific uncatalyzed thermal (sigmatropic) as well as base or transition metal catalyzed hydrogen shifts. The substances synthesized will be examined from a spectroscopic as well as structure-function point of view. A new structural model (the B-K Site Model) for rhodopsin is proposed and biological evaluation of several of the new retinals should provide a test of this model. Deuterated and hydrogen shifted retinoids will be used to test the concept that cis-trans isomerization processes, such as that observed in photobleaching and in the thermal 11-cis to all-trans-retinal conversion, involve hydrogen shifts from allylic positions of the retinoids.